Modern PCs are certainly marvels of technology–and yet for all their advances, computers still do crazy, inexplicable things. With the average machine, there’s enough mystery to keep Sherlock Holmes or Miss Marple hopping for a month–and enough frustration to make the average user want to commit murder most foul.

Computing mysteries tend to be less “Who dunnit?” and more “Why won’t it?” For example, you may have puzzled over why Windows obstinately refused to let you delete a stalled print job, or wondered why you couldn’t find the file you just downloaded. But worry not: We’ve rounded up these and other mindbogglers of the PC universe–and solved them for you.